Elevator systems are provided with safety systems for safe operation. Said safety systems typically consist of safety elements connected in series. Said safety elements can for example monitor the condition of shaft doors or elevator car doors. Electromechanical safety circuits or else bus-based safety circuits are known for this. The safe operation of such bus-based safety circuits is checked regularly. The structure and testing methods of such bus-based safety circuits are known for example from EP 1159218 A1, WO 2010/097404 A1 or WO 2013/020806 A1. However, it is not clear from this prior art whether or to what extent safety is ensured when temporary participants, such as a manual control device for controlling the elevator system during maintenance or an input device in which configuration settings of the safety system can be set, are connected and disconnected.